全文获取类型
收费全文 | 33965篇 |
免费 | 4582篇 |
国内免费 | 3003篇 |
专业分类
电工技术 | 2588篇 |
技术理论 | 7篇 |
综合类 | 4509篇 |
化学工业 | 990篇 |
金属工艺 | 418篇 |
机械仪表 | 1720篇 |
建筑科学 | 8620篇 |
矿业工程 | 581篇 |
能源动力 | 439篇 |
轻工业 | 514篇 |
水利工程 | 305篇 |
石油天然气 | 745篇 |
武器工业 | 1331篇 |
无线电 | 6761篇 |
一般工业技术 | 2367篇 |
冶金工业 | 636篇 |
原子能技术 | 528篇 |
自动化技术 | 8491篇 |
出版年
2024年 | 220篇 |
2023年 | 565篇 |
2022年 | 1103篇 |
2021年 | 1147篇 |
2020年 | 1147篇 |
2019年 | 990篇 |
2018年 | 917篇 |
2017年 | 1070篇 |
2016年 | 1300篇 |
2015年 | 1494篇 |
2014年 | 2446篇 |
2013年 | 2042篇 |
2012年 | 2694篇 |
2011年 | 2917篇 |
2010年 | 2471篇 |
2009年 | 2434篇 |
2008年 | 2343篇 |
2007年 | 2625篇 |
2006年 | 2162篇 |
2005年 | 1747篇 |
2004年 | 1394篇 |
2003年 | 1173篇 |
2002年 | 930篇 |
2001年 | 804篇 |
2000年 | 703篇 |
1999年 | 561篇 |
1998年 | 399篇 |
1997年 | 295篇 |
1996年 | 283篇 |
1995年 | 225篇 |
1994年 | 190篇 |
1993年 | 144篇 |
1992年 | 143篇 |
1991年 | 80篇 |
1990年 | 71篇 |
1989年 | 66篇 |
1988年 | 55篇 |
1987年 | 33篇 |
1986年 | 28篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1959年 | 12篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
基于扩展分形和CFAR特征融合的SAR图像目标识别 总被引:3,自引:0,他引:3
研究了多信息融合技术在SAR图像目标识别中的应用。将扩展分形特征(Extended Fractal)与双参数恒虚警特征(Double Parameter CFAR)形成的多信息进行融合处理。运用Dempster-Shafer证据理论,在决策层对SAR图像中的像素进行识别分类。实验结果表明通过融合对像素分类的准确性明显好于单特征的检测结果,减少了虚警概率,提高了系统的识别能力。 相似文献
2.
Hong Jeong Jeong‐Ho Park 《International Journal of Adaptive Control and Signal Processing》2002,16(1):1-23
Tracking targets of interest is one of the major research areas in radar surveillance systems. We formulate the problem as incomplete data estimation and apply EM to the MAP estimate. The resulting filter has a recursive structure analogous to the Kalman filter. The advantage is that the measurement‐update deals with multiple measurements in parallel and the parameter‐update estimates the system parameters on the fly. Experiments tracking separate targets in parallel show that tracking maintenance ratio of the proposed system is better than that of NNF and RMS position error is smaller than that of PDAF. Also, the system parameters are correctly obtained even from incorrect initial values. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
3.
Somsak Vanit-Anunchai Jonathan Billington Guy Edward Gallasch 《International Journal on Software Tools for Technology Transfer (STTT)》2008,10(1):29-56
State space explosion is a key problem in the analysis of finite state systems. The sweep-line method is a state exploration
method which uses a notion of progress to allow states to be deleted from memory when they are no longer required. This reduces
the peak number of states that need to be stored, while still exploring the full state space. The technique shows promise
but has never achieved reductions greater than about a factor of 10 in the number of states stored in memory for industrially
relevant examples. This paper discusses sweep-line analysis of the connection management procedures of a new Internet standard,
the Datagram Congestion Control Protocol (DCCP). As the intuitive approaches to sweep-line analysis are not effective, we
introduce new variables to track progress. This creates further state explosion. However, when used with the sweep-line, the
peak number of states is reduced by over two orders of magnitude compared with the original. Importantly, this allows DCCP
to be analysed for larger parameter values.
Somsak Vanit-Anunchai was partially supported by an Australian Research Council Discovery Grant (DP0559927) and Suranaree
University of Technology.
Guy Edward Gallasch was supported by an Australian Research Council Discovery Grant (DP0559927). 相似文献
4.
磁偏转电子枪研制核靶 总被引:3,自引:3,他引:0
文章叙述了磁偏转电子枪的原理和结构以及用EQD-3型电子枪研制各种核靶的工艺过程。 相似文献
5.
STATIONARY AND NON-STATIONARY STATE SPACE MODELS 总被引:1,自引:0,他引:1
Abstract. The concepts of time invariance, stationarity, non-stationarity and immemorial time are considered for state space models (SSMs). Necessary and sufficient conditions for stationarity are given and connected with standard conditions. Expressions are given for the unconditional mean and covariance matrix of the state of a time-immemorial SSM. Application of the results is made to a variety of theoretical and empirical models and the initialization of the Kalman filter in the non-stationary case and for the ARIMA ( p, d, q ) model. 相似文献
6.
T. Bag 《Information Sciences》2006,176(19):2910-2931
In this paper, definitions of strongly fuzzy convergent sequence, l-fuzzy weakly convergent sequence and l-fuzzy weakly compact set are given in a fuzzy normed linear space. The concepts of fuzzy normal structure, fuzzy non-expansive mapping, uniformly convex fuzzy normed linear space are introduced and fixed point theorems for fuzzy non-expansive mappings are proved. 相似文献
7.
CIE TC8‐01 has adopted a new color appearance model: CIECAM021 replaces the CIECAM97s.2 The new model consists of a number of refinements and simplifications of the CIECAM97s color appearance model. This article describes further tests to the robustness of the forward and reverse modes. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 99–106, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20087 相似文献
8.
通过对高抗冲聚苯乙烯树脂出现产品落锤指标偏低问题的分析,从橡胶配量及其粒径大小上进行了改进,同时改进了工艺操作,采取了提高反应釜搅拌速度、降低乙苯浓度等措施。结果产品合格率达到99%以上,优级品率达到98%以上。 相似文献
9.
Alekseevskii-Tate revisited:An extension to the modified hydrodynamic theory of long rod penetration
LAN Bin & WEN HeMing CAS Key Laboratory for Mechanical Behavior Design of Materials University of Science Technology of China Hefei China 《中国科学:信息科学(英文版)》2010,(5)
The modified hydrodynamic theory of long rod penetration into semi-infinite targets was established independently by Alek-seevskii and Tate over forty years ago and since then many investigators contributed much to the development of the high speed penetration mechanics.However,in all the models proposed so far,the target resistance Rt is not well defined and usually determined by adjusting it until the predicted depth of penetration comes to an agreement with experimental data.In this paper,assumptions are... 相似文献
10.
为了建立多维应力、应变空间的弹塑性本构关系,将一般加载规律一维全量理论的简单弹塑性模型推广到一般加载规律的多维增量理论,并且给出应力空间的加载函数和应变空间的加载函数以及它们之间的正确的变换关系.在此基础上,在应变空间中建立了推导一般加载规律的多维增量理论的本构关系的一种途径.应用这种途径,从应变空间的加载函数出发,推导了等向强化材料的一般加载规律的弹塑性本构关系.理论和实例表明,这种途径对等向强化材料、随动强化材料、理想弹塑性材料和热弹塑性问题都适用. 相似文献